Madrid - World No 4 Jon Rahm kicked off his bid for a first professional title on home soil with a five-under-par 67 at the Spanish Open on Thursday, while Spanish amateur Victor Pastor thrilled the home crowds.
Scotland's Marc Warren and Irishman Paul Dunne lead the way by a single stroke on six under, but all eyes were on Spaniard Rahm after his fourth-placed finish at last week's Masters.
The 23-year-old fired four birdies and an eagle at the 18th hole despite suffering from jet-lag after travelling from Augusta, where he finished four strokes behind winner Patrick Reed.
"I'm a lot better than I expected, hopefully tomorrow it keeps going good because jet-lag tricks you sometimes," he said.
"It feels great. To be honest, I would have taken anything under par given the fact that I played a lot better than I expected to play.
"Especially off the tee, my driving was really, really good today, I did not expect that. My long game was amazing."
Rahm is hoping to follow in the footsteps of compatriots Seve Ballesteros, Sergio Garcia and Miguel Angel Jimenez in winning his home event.
His Masters surge was the first time he has threatened at a major, but a dramatic rise has seen Rahm win four tournaments after turning pro in 2016 and become a shoo-in for September's Ryder Cup in France.
Meanwhile, Pastor showed himself to be an unlikely contender as the world No 1 958 matched Rahm's 67, including an incredible eagle on his opening hole.
"I had a really bad tee-shot and ended up on the 18th or 16th fairway," he said of his errant start on the 10th tee.
"I had 240 yards to the green and I hit a tremendous three wood and hit a really good putt from ten to 12 metres, so it was a very good start."
Co-leader Dunne will know how Pastor is feeling, having led the 2015 British Open as an amateur heading into the final round.
The reigning British Masters champion eagled the final hole to sign for a 66 and draw level with Warren.
"I'm pretty pleased," Dunne said. "I find the greens quite tricky to read out there, especially on the front nine, so it was nice to get a couple of putts go in on the back nine and give myself a climb up the leaderboard."
Popular Englishman Andrew 'Beef' Johnston is the defending champion after winning the 2016 title, as the tournament wasn't held last year.
The 29-year-old showed few signs of rust as he returned from a month-long absence with a four-under round of 68.
"I felt a bit achey coming in, but my brain was working so that helps," Johnston said.
"I had a nice break and I'm just looking forward to getting on and trying to defend.
"I went down to see the Anthony Joshua fight in Cardiff one weekend and I just hung out with mates. Caught up, went for some food and chilled out, a few lazy days. A lot of Netflix."
Leading first-round scores from the European Tour's Spanish Open at the Centro Nacional de Golf in Madrid on Thursday (GBR/IRL unless stated; par 72; 'a' denotes amateur):
66 - Marc Warren, Paul Dunne
67 - Jason Norris (AUS), Jon Rahm (ESP), Jonathan Thomson, Julien Guerrier (FRA), Erik van Rooyen (RSA), Matthias Schwab (AUT), Victor Pastor (ESP/a), Alexander Bjork (SWE), Henric Sturehed (SWE), Callum Shinkwin, Aaron Rai
68 - Richard Sterne (RSA), Pedro Oriol (ESP), Thorbjorn Olesen (DEN), Andrew Johnston, Trevor Fisher Jr (RSA), Nacho Elvira (ESP), Paul Waring, Brett Rumford (AUS), Sebastian Heisele (GER)